A magnetic tunnel junction is an integrated circuit component having two conductive magnetic electrodes separated by a thin non-magnetic tunnel insulator material (e.g., dielectric material). The insulator material is sufficiently thin such that electrons can tunnel from one magnetic electrode to the other through the insulator material under appropriate conditions. At least one of the magnetic electrodes can have its overall magnetization direction switched between two states at a normal operating write or erase current/voltage, and is commonly referred to as the “free” or “recording” electrode. The other magnetic electrode is commonly referred to as the “reference”, “fixed”, or “pinned” electrode, and whose overall magnetization direction will not switch upon application of the normal operating write or erase current/voltage. The reference electrode and the recording electrode are electrically coupled to respective conductive nodes. Electrical resistance between those two nodes through the reference electrode, insulator material, and the recording electrode is dependent upon the magnetization direction of the recording electrode relative to that of the reference electrode. Accordingly, a magnetic tunnel junction can be programmed into one of at least two states, and those states can be sensed by measuring current flow through the magnetic tunnel junction. Since magnetic tunnel junctions can be “programmed” between two current-conducting states, they have been proposed for use in memory integrated circuitry. Additionally, magnetic tunnel junctions may be used in logic, sensors, oscillators or other circuitry apart from or in addition to memory.
The overall magnetization direction of the recording electrode can be switched by a current-induced external magnetic field or by using a spin-polarized current to result in a spin-transfer torque (STT) effect. Charge carriers (such as electrons) have a property known as “spin” which is a small quantity of angular momentum intrinsic to the carrier. An electric current is generally unpolarized (having about 50% “spin-up” and about 50% “spin-down”electrons). A spin-polarized current is one with significantly more electrons of either spin. By passing a current through certain magnetic material (sometimes also referred to as polarizer material), one can produce a spin-polarized current. If a spin-polarized current is directed into a magnetic material, spin angular momentum can be transferred to that material, thereby affecting its magnetization orientation. This can be used to excite oscillations or even flip (i.e., switch) the orientation/domain direction of the magnetic material if the spin-polarized current is of sufficient magnitude.
An alloy or other mixture of Co and Fe is one common material proposed for use as a polarizer material and/or as at least part of the magnetic recording material of a recording electrode in a magnetic tunnel junction. A more specific example is CoxFeyBz where x and y are each 10-80 and z is 0-50, and may be abbreviated as CoFe or CoFeB. MgO is a suitable material for the non-magnetic tunnel insulator.
Tunnel insulator materials are often crystalline, and are desired to have a body-centered-cubic (bcc) 001 lattice.
Tunnel insulator and polarizer materials may be deposited using any suitable methodology (e.g., physical vapor deposition). One technique usable to ultimately produce the bcc 001 lattice in both tunnel insulator and adjacent polarizer material includes initially forming cobalt-and-iron-containing material of the polarizer to be amorphous and upon which tunnel insulator material (e.g., MgO) is deposited. During and/or after the depositing, the cobalt-and-iron-containing material and the tunnel insulator may each achieve a uniform bcc 001 lattice structure.